The invention relates, in general, to data storage, and more particularly to compact storage of both text and graphics.
Computer displays frequently require both mixed text and graphics on the same screen. When storing information of this type, some form of compression is necessary to conserve memory space. Compression schemes can be highly effective due to the inherent redundancy of the information. For example, large portions of a typical computer display are blank. An example of a compression method which is suited to digital image compression is the "Tagged Image File Format" or "TIFF" described in a document "A GUIDE TO THE TAGGED-IMAGE FILE FORMAT", reference number 5958-4196, published Feb. 4, 1987 by Hewlett-Packard Company, Greeley, Colo. This method uses a raster scan of the digital image, compressing the individual pixels as a bit-map. The "TIFF" coding method is extremely flexible and is used for images of every conceivable type. Of necessity, however, it is relatively complex and can require a high computing overhead to perform.
There is a need for a simple, and efficient compression scheme which will allow storage of the information on a computer screen and subsequent re-display of that information later while still using a minimum amount of memory. The method should be simple enough to use with an 8-bit microcomputer.